1. Field of Invention
The present invention relates to water control gates and inflatable dams for control of water for use in conjunction with, but not limited to, dam spillways, hydroelectric projects, flood control structures, river diversions, irrigation canal check structures, roadway water barriers, levee crossings, parking garage water barriers, to inflatable actuators therefore, to inflatable actuators in general, to reinforced elastomeric hinges therefore, and to inflatable articles in general such as actuators for machines such as presses, dunnage bags, inflatable jacks, collapsible hoses and the like. The inflatable actuators herein disclosed may have many other applications, particularly where low cost, long life and reliability are important.
2. Description of Related Art
Various attempts have been made to develop economical water control gates. In many instances, the most economic water control gates are air actuated bottom hinged gates and inflatable dams. As but one advantage, the position of a plurality of water control gates can be infinitely adjusted by adjustment of the inflatable actuator pressures. Various patents relating to air-actuated bottom hinged gates and relating to inflatable dams are attached to this application and are hereby incorporated by reference. Various other materials relating to what may be prior art are also attached and are also hereby incorporated by reference. Hydraulically or mechanically operated gates are generally more expensive than the aforementioned air operated gates and inflatable dams, particularly if the cost of construction of required associated piers, equipment platforms, service cranes and bridges is accounted for. The limitations heretofore of inflatable dams have included high stresses at the downstream fold. In the case of inflatable dams manufactured from a single flat sheet, these stresses in the elastomeric material may occur with the inflatable dam in the inflated configuration. Failure may result due to a combination of tensile stresses in the outermost layers due to bending of the dam body in conjunction with flow induced vibration associated with a rounded flexible surface from which flow may separate in an oscillatory manner. In the case of inflatable dams manufactured as a folded sheet, high tensile stresses may result in both the elastomeric inner-liner and in the inner most plies of reinforcing fabric when the dam is inflated. These high stresses in the reinforcing fabric may dictate that a high elongation fiber such as nylon be used even though nylon may have inferior long term water resistance compared to polyester, for example. The high stresses may generally lower the factor of safety or increase the overall cost of such an inflatable dam. Furthermore, even if reinforcement failure is avoided, high tensile stresses in the elastomeric inner-liner may result in cracking which may cause air leakage into the fiber reinforcement. This fiber reinforcement may be exposed at other locations resulting in gradual but undesirable air loss from the inflatable dam. Furthermore, inter-ply pressures may be increased, which may result in long-term oxygen degradation of the dam body and the susceptibility of the outer cover to blistering.
The limitations heretofore of bottom hinged air actuated gates have been the requirement for custom field fitting of seals, the requirement for heating of abutment plates during icing conditions, and the somewhat higher cost, relative to benefits, of gates for low damming heights such as 2 meters or less. Specifically, with respect to gates for low damming heights such as 2 meters or less, the designs of the prior art have generally fallen into two categories. In the first category are designs such as those described in U.S. Pat. No. 5,092,707 to Obermeyer, U.S. Pat. No. 5,538,360 to Obermeyer, and U.S. Pat. No. 5,713,699 to Obermeyer et al. The designs of this first category call for a secondary vulcanization process for joining of the seam under the clamp bar. Secondary vulcanization processes (an additional, second vulcanizing process) may entail extra expense and may result in joints, which are less reliable than those created using a single stage vulcanization (merely one vulcanizing process) used in accordance with at least one embodiment of the present invention. Furthermore, said secondary vulcanization process can, at best, provide an elastomeric seal under the clamp bar. Continuity of circumferential reinforcement around the inflatable portion of the air bladder may not be accomplished by simply bonding and sealing the clamped joint in a secondary vulcanization step. Although the use of a wedge type clamping system as disclosed in U.S. Pat. No. 5,709,502 to Obermeyer eliminates the requirement for a vulcanized joint under the clamp system, the clamp system itself may become relatively expensive as damming heights become lower.
A disadvantage common to both inflatable dams with clamped unvulcanized joints and to air actuated bottom hinged gates with vulcanized joints is the phenomenon of creep of the elastomer compressed under the clamp system. Proper functioning of each system may generally rely on sufficient compressive stress under the clamp to prevent air leakage. The higher the compressive stress, the higher the associated shear stress becomes which, in turn, may lead to increased creep rates. Thus, the more securely such a clamp is tightened, the more often it may require re-tightening. Proper maintenance requires a careful balance between insufficient tightening which may result in leakage or system failure and excessive tightening which may lead to high rates of creep and also to system failure.
Conventional inflatable dams may also be subject to vibration during over-topping conditions. Attempts have been made to aerate a nappe, leaving a fin by varying the dimensions of the fin or by providing discrete fins. Even with these mitigative measures, vibration may still be a problem under certain flow conditions.
Additionally, the air fittings most commonly used in conjunction with air actuated bottom hinged gates and inflatable dams of the prior art may require protection during installation and may include sharp-machined edges. These sharp edges of these air fittings may damage or even penetrate adjacent air bladders if several air bladders are stacked for shipment or if such a fitting were to be installed prior to rolling up a long inflatable dam.
Additionally, air actuated bottom hinged gates and inflatable dams of existing systems may generally not be well suited for vehicle or pedestrian traffic when in the lowered or deflated position. Conventional bottom hinged water control gates may be fitted with irregularly shaped hinges and reinforcing ribs which may not obstruct water flow but may pose a hazard or even a barrier to vehicular or pedestrian traffic.
Conventional bottom hinged water control gates have also incorporated restraining straps, which may protrude from beneath the lowered gate panels. The protrusion of said restraining straps may be hazardous to pedestrian traffic. Such protruding restraining straps may be damaged by vehicular traffic. Furthermore, the protrusion of these restraining straps may be undesirable in certain water control applications even where traffic is not a design criterion.
Conventional bottom hinged roadway and walkway water barriers have in some cases utilized mechanical hinges, which may be subject to leakage of water and corrosion and in some cases have used mechanical actuators, which may be subject to corrosion. Additionally, such mechanical hinges may require precise alignment, which may be expensive.
Inflatable articles such as lifting bags (inflatable jacks), dock bumpers, hoses, inflatable dams and spillway gate actuators are typically manufactured by one of two methods. In the first method an internal mandrel or tool is used to define an internal surface with rounded edges. This method requires a secondary bonding operation or special device to seal the opening through which the mandrel or tool may be removed. In the second method, the interior is allowed to simply fold flat while the interior surfaces are prevented from bonding by means of a release film. This results in extreme stress concentrations of the inner liner in the inflated condition and, with multiple layers of reinforcement, extremely uneven load sharing between the layers of reinforcement. A third method utilizes three dimensional soluble mandrels of eutectic salts, aluminum, paper mache, etc. This type of soluble mandrel is expensive, time consuming, and in the case of salt, very fragile.
Conventional spillway and navigation dam gates may be fitted with individual actuators or, in some instances, may be lifted to raised and locked positions one by one from a work boat or overhead cable hoist. Lifting the gates from overhead with either a boat or cableway may require dangerous work by highly skilled operators. Individual actuators may be too expensive for some projects. The use of very long spans of actuated water control gates in lieu of levees has often been cost prohibitive with existing systems.
Conventional spillway gates often use nappe breakers to prevent vibration under conditions of small amounts of over-topping. Such nappe breakers are generally made of steel and are easily damaged by winter ice flows.